1. Field of the Invention
The present invention relates to a refrigerant circulating system for a refrigerating and air conditioning system or the like using a refrigerant made of a nonazeotropic mixture including several types of refrigerants.
2. Description of the Conventional Art
FIG. 67 shows a conventional refrigerating and air conditioning system using a nonazeotropic refrigerant mixture including several types of refrigerants as disclosed, for example, in Examined Japanese Patent Publication No. Hei. 6-12201. In FIG. 67, a compressor 1, a heat exchanger 2 at the load side, the main throttle devices 3 and 4, and a heat exchanger 5 at the heat source side are connected by refrigerant pipings to form a main circuit for a refrigerating cycle. To the top part of the refrigerant rectifying column 8, a column-top storing tank 11 is connected by a refrigerant piping 17 and a refrigerant piping 18 with a refrigerant source 9 arranged thereon. A column-bottom storing tank 12 is connected to the bottom part of the above-mentioned refrigerant rectifying column 8 by a refrigerant piping 19 and a refrigerant piping 20 with a heating source 10 disposed thereon.
Between the heat exchanger 2 at the load side and the heat exchanger 6 at the heat source side, the column-top storing tank 11 is connected by a refrigerant piping 21 on which an opening/closing valve 15 is disposed, and the column-bottom storing tank 12 is connected by the refrigerant piping 22 on which an opening/closing valve 16 is disposed. To the upstream side of the heat exchanger 6 at the heat source side, the column-top storing tank 11 is connected by a refrigerant piping 23 having an auxiliary throttle device 5 and an opening/closing valve 13 disposed thereon, and the column-bottom storing tank 12 is connected by a refrigerant piping 24 having an auxiliary throttle device 5 and an opening/closing valve 14 disposed thereon. Then, a flow-out port from the column-top storing tank 11 to the refrigerant piping 23 is provided in the bottom area of the column-top storing tank 11, and a flow-out port from the column-bottom storing tank 12 to the refrigerant piping 24 is provided in the bottom area of the column-bottom storing tank 12.
In the construction described above, the vapor of the nonazeotropic mixed refrigerant (hereinafter referred to as "the refrigerant") at a high temperature and a high pressure as compressed by the compressor 1 flows in the direction of the arrow mark A, so as to be condensed by the heat exchanger at the load side to feed into the main throttle device 3. In a normal operation, the opening/closing valves 15 and 16 are kept closed, so that the refrigerant flows as it is into the main throttle device 4, and the refrigerant which has reached a low temperature and a low pressure is evaporated by the heat exchanger at the heat source side 6 and is fed back into the compressor 1.
In a case where the composition of the refrigerant flowing in this main circuit is to be changed, the opening/closing valves 13 and 15 are closed, and the opening/closing valves 14 and 16 are opened so that the composition of the refrigerant flowing in the main circuit is changed into a composition very rich in constituents at a high boiling point. Then, a part of the refrigerant flowing in the main circuit which has come out of the main throttle device 3 flows into the opening/closing valve 16 which is being kept open while the remainder of the refrigerant flows into the main throttle device 4 and flows in the same circuit as in the normal operation. On the other hand, the refrigerant which has flown into the opening/closing valve 16 enters the column-bottom storing tank 12. Some part of the refrigerant which has thus entered the column-bottom storing tank 12 flows into the auxiliary throttle device 5 via the opening/closing valve 14 which is being kept open and then flows together with the refrigerant flowing in the main circuit at the upstream side of the heat exchanger at the heat source side 6, and the remaining part of the refrigerant flows into a refrigerant piping 20 having the heating source 10 disposed thereon, where the refrigerant is heated and thereby turned into vapor, the refrigerant moving upward in the refrigerant rectifying column 8. At such a time, the refrigerant liquid stored in the column-top storing tank 11 moves downward in the refrigerant rectifying column 8 via refrigerant piping 17 so as to contact with the refrigerant vapor moving upward in the refrigerant rectifying column 8 to conduct a gas-liquid contact, thereby producing a rectifying effect as it is generally known.
In this manner, the refrigerant vapor becomes richer in constituents at low boiling points as it moves upward, and the refrigerant vapor is led into a refrigerant piping 18 having a cooling source 9 disposed thereon, where the refrigerant vapor is liquefied and stored in the column-top storing tank 11 since the opening/closing valve 13 is closed. Thus, the rectifying process just described is repeated until only the refrigerant very rich in constituents at low boiling points is stored in the column-top storing tank 11. Therefore, the composition of the refrigerant which flows in the main circuit is made very rich in constituents at a high boiling point.
On the other hand, to make the composition of the refrigerant flowing in the main circuit rich in constituents at low boiling points, the opening/closing valves 13 and 15 are kept open while the opening/closing valves 14 and 16 are kept closed. Then, a part of the refrigerant flowing in the main circuit which comes out of the main throttle device 3 flows into the column-top storing tank 11 via the opening/closing valve 15. However, since the opening/closing valve 13 also opens, a part of the refrigerant flowed into the column-top storing tank 11 flows together with the refrigerant flowing in the main circuit through the refrigerant piping 23 and the auxiliary throttle device 5. The remaining part of the refrigerant flows into the refrigerant rectifying column 8 by way of the refrigerant piping 17 and moves downward. At this time, a part of the refrigerant stored in the column-bottom storing tank 12 is heated by the heating source 10 so as to move upward in the refrigerant rectifying column 8, thereby getting into its gas-liquid contact with the refrigerant fluid moving downward in the same refrigerant rectifying column 8 and performing the rectifying process. In this manner, the downward-moving refrigerant liquid gradually become richer in constituents at a high boiling point, and, since the opening/closing valve 14 is closed, the refrigerant liquid is stored in the column-bottom storing tank 12. Then, as this rectifying process is repeated, only the refrigerant very rich in constituents at a high boiling point is stored in the column-bottom storing tank 12. Therefore, the composition of the refrigerant flowing in the main circuit is made very rich in constituents at low boiling points. Other techniques for circulating a nonazeotropic mixed refrigerant has been known to be taught, for example, in Examined Japanese Patent Publication Nos. Hei. 5-40221 and Japanese Patent Publication No. 4-23625.
In the conventional refrigerant circulating system for the refrigerating and air conditioning system described above, the rectified constituents are stored in the refrigerant rectifying column. Consequently, the conventional refrigerant circulating system can not cope with a sharp change of the pressure such as a time of a start-up of the compressor where the density of the refrigerant is not constant in the refrigerant circuit. In addition, the complicated structure and large size of the refrigerant rectifying column itself require a high cost.
Further, such a conventional refrigerating and air conditioning system does have no means for detecting or judging the composition of the refrigerant and cannot therefore be controlled in a manner suitable for its composition. Accordingly, it is not always to be possible to perform an efficient operation of the system. In addition, the conventional refrigerating and air conditioning system has to be controlled in very complicated operations.